When Prof. Crater gets stunned on the planet the scene is run in fast forward, for some unknown reason. It looks really weird and really awful.

Great Moment :

The creature as Bones, trying to convince everybody not to hunt it down.

Body Count :

Five

Factoid :

The great bird of the galaxy which Sulu refers to is a common nickname for Gene Roddenberry!

This was the first episode of Star Trek ever aired. It was chosen for that honour largely because unlike The Corbomite Maneuver it had a planet for the characters to visit and a proper "monster" to kill crew members, unlike the pilot Where No Man Has Gone Before it didn't have a lot of exposition, and it wasn't as sexually themed as Mudd's Women.

Thanks at least in part to the explosion which happens near to Kirk in this episode and in the later Arena, Will Shatner has suffered from a constant ringing in his ears ever since.

Plotline

The Enterprise visits M-113 on a supply trip for the scientific station there, which comprises Doctor Robert Crater and his wife, Nancy. Nancy is an old flame of Doctor McCoy, and he is looking forward to seeing her again. The Craters have been on M-113 for the last five years, conducting archaeological surveys of the ruins there. Kirk and McCoy beam down with Crewman Darnell, but on meeting the couple each man sees Nancy as a different woman - to McCoy, she is identical to the young Nancy he remembers whilst to Kirk she appears to be a much older version of the same woman. Darnell, on the other hand, sees a very different woman who looks like somebody he knew on Wrigley's Pleasure Planet.

Doctor Crater seems very abrupt with the crew, wanting them to leave as soon as possible and saying that the only supplies they need are new salt tablets, necessary in the planet's hot climate. As they talk Darnell goes outside with Nancy and she leads him off away from the area. A scream is heard and Darnell is subsequently found dead, his face covered in odd splotches.

Nancy claims she saw Darnell eat a sample of a local plant, which is poisonous. An upset Kirk beams back with the body so that McCoy can examine it. He finds no trace of poison, but there is one oddity - Darnell's body doesn't have a trace of salt anywhere in it.

Kirk beams back down with two Crewmen to investigate further. Crater continues to act oddly, running off to look for Nancy. Two more Crewmen subsequently die, killed by Nancy. She changes her form to imitate Crewman Green and beams back to the ship with the rest. Aboard the ship "Green" wanders around, apparently looking for supplies of salt. His behaviour seems strange to the others, but he doesn't stay in one place long enough to arouse more than curiosity. He kills several people by draining their bodies of salt, much as he did on the planet.

Kirk beams down again to talk to Crater. The Doctor fires on him, but Kirk is able to stun him with his phaser. Under questioning Crater admits that Nancy is dead; what they met was a creature native to the planet, a being who can project an image to others in order to disguise himself. He says that the species was once very common on the planet, but now there is only one remaining. It has an insatiable desire for salt, which it needs to survive. There is almost no salt left on the planet, which is why the creatures died off. Crater used his supplies of the mineral to pacify the creature and lived with it after his wife died.

meanwhile the creature imitates McCoy, mixing with the other officers. Eventually it kills Crater and goes to McCoy's room, changing once again into Nancy and pleading for help. Kirk and Spock work out where it is and rush to the rescue, but McCoy can't quite bring himself to fire on the creature even as it attacks Kirk. Spock attacks the creature, demonstrating that even his huge strength cannot harm it - something that Nancy couldn't possibly endure. A distraught McCoy finally fires, killing the creature.

Analysis

Not a bad effort, really, all in all. Whilst it does do the whole "Monster on the prowl" thing, the story does give us a credible reason why the creature does what it does - it's the last of its kind, alone, desperate for the food it needs, and the only real source of that food is walking around inside us.

You can speculate somewhat about just how this creature lived. Crater talks of great herds of them roaming the plains. Yet it clearly seems to be a predator, since it's evolved to suck salt out of other living things through the skin. The copying defence would also suit a predatory animal very well. This doesn't sit very well with the idea of large herds of the creatures sweeping majestically across the plains... predators tend to be solitary creatures, or at least limited to small packs. Certainly the fact that the creature seems to need to kill at least once a day or so would indicate that a large population of them moving together would require huge numbers of prey animals to feed on, which seems unlikely. It could be that Crater is simply romanticising the creature, or perhaps it lied to him about itself?

A couple of other oddities. For one, the creature clearly has the ability to control what it looks like consciously. It's not a matter of just projecting some telepathic command to "see something harmless", the creature deliberately chooses to appear as a specific person on multiple occasions. So given that, you have to wonder why it decided to project three different images to three different men who were in the same room together at the start. If Darnell had simply said "what lovely blonde hair you have!" right up front, the whole thing could easily have unravelled right there.

For another thing, the creature is obviously intelligent enough to actually pass for the person it imitates. Yes, it's a bit goofy in how it talks sometimes, but it is able to sit in on a conference as McCoy and make intelligent comments, so it's a sentient being. Given this, why didn't it simply ask for the salt in the first place? As long as it has a supply it is completely harmless to people, and the Federation would want the chance to study it, ask it questions, etc. There's every potential for a mutually beneficial relationship there, yet the creature never thinks to try. We could argue that it doesn't trust outsiders but it's been living with Crater for years in exchange for salt, so it's clearly able to get over any distrust and form a relationship. And surely Crater of all people should know what a huge discovery this is and how the Federation would value it. It's a gaping plot hole that really destroys the whole premise of the episode.

Special Edition

The remastered version has the usual improved effects, including new shots of the Enterprise and a new M-113 planet.